For many reasons, not the least of which is the relatively high cost for prime movers, it is desirable to be able to employ a single prime mover in conjunction with a plurality of work implements. Historically, the lifting and tilting mechanisms provided by prime movers connected directly to the individual work implements. To change work implements was, at best, a difficult and time consuming chore that would require two workmen. One of the workmen manipulated the prime mover, as well as the lifting and tilting mechanisms presented therefrom. The second workman manually manipulated the work implement in order to assist in effecting the connections between the lifting and tilting mechanisms and the work implement and also served as a "spotter" to observe those areas which would be blocked from the view of the workman manipulating the prime mover by the mechanism presented from the prime mover to effect the connection with the work implement. As a spotter, the second workman thus guided the workman driving the prime mover. Accordingly, it was potentially dangerous to life, limb and property every time work implements had to be changed when utilizing the historic arrangements to effect such a change.
The normal difficulties attendant upon securing a work implement directly to the lifting and tilting mechanisms presented from the prime mover forced efficient operators to minimize the number of times the work implements are changed and to provide a relatively level area upon which to store the work implements inasmuch as the most efficient performance of the inefficient task of manually changing work implements could only occur if both the work implement and the prime mover were on level terrain.
The many disadvantages of demountably attaching work implements manually, and directly, to the lifting and tilting mechanisms on a prime mover were obviated by the system disclosed in U.S. Pat. No. 3,417,886, and as a result that system has received wide acceptance over the years.
One of the principal disadvantages of the system to which U.S. Pat. No. 3,417,886 is directed does not involve the system itself. Rather, the disadvantage results from the purchasing procedure imposed upon users of more than one prime mover and the various work implements demountably attachable thereto. Such users do not normally acquire all their prime movers at the same time. Generally, a user having more than one prime mover will have acquired them over the years, and such sporadic purchases are frequently made on the basis of the lowest cost. Hence, such entities often own prime movers which originate from more than one manufacturer as well as work implements which also originate from a number of different manufactures.
Modest dimensional differences between the attachment points for the lifting and tilting mechanisms on prime movers originating from different manufacturers require a separte coupling member for attachment to the prime mover from each different manufacturer, as well as for each different size and model of prime mover from even one manufacturer. Each different coupling member attached to the prime movers similarly requires that a separate and distinct coupling member be attached to the work implements to be employed by each prime mover. Hence, while the concept for utilizing coupling systems incorporating the concepts of U.S. Pat. No. 3,417,886 did definitely have its advantages, the realities of dimensional differences between equipment acquired from different manufacturers precluded total acceptance of that system.
The foregoing difficulties have been further compounded by the recent trend for prime mover manufactures to make both four-arm lifting and tilting mechanisms and three-arm lifting and tilting mechanisms available as alternative options. This further compounds the number of coupling elements required to be made available not only for attachment to various prime movers but also for attachement to several work implements.
The difficulties are more readily appreciated when one recognizes the fact that the coupler element utilized by each work implement is normally affixed relatively permanently to that work implement.
The prior known coupling assemblies also utilize the locking mechanism, and perhaps some modest vertical contact between the coupling elements, to assist in the transfer of both static and dynamic loading between the coupling elements. Arrangements of that nature impart highly concentrated loading stresses to the structure of the coupling elements, which can be deleterious to the coupling assembly.
Finally, most known attempts to obviate the foregoing adverse characteristics of prior known coupler assemblies result in locating the center of gravity of the work implement more forwardly of the prime mover than desirable.